<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title>深层次探究居中</title>
		<style type="text/css">
			.fu{
				width: 400px;
				height: 400px;
				background-color: blue;
				display: flex;
				justify-content: center;
				align-items: center;
			}
			.zi{
				width: 200px;
				height: 200px;
				display: flex;
				border: 1px solid red;
				flex-wrap: wrap;
			}
			.zi span{
				width: 100px;
				height: 100px;
				background-color: greenyellow;
				text-align: center;
				line-height: 100px;
			}
		</style>
	</head>
	<body>
		<div class="fu">
			<div class="zi">
				<span>1</span>
				<span>2</span>
				<span>3</span>
				<span>4</span>
			</div>
		</div>
	</body>
</html>
